EP0231398B1 - Continuous mixing and shearing mill - Google Patents

Abstract

A continuous shearing rolling mill is disclosed with improved roll drive system, roll temperature control, surface and groove geometries of the shearing rolls, and material discharge and pelletizing devices on the front roll.

Description

The invention relates to a continuous mixing and shearing mill for plasticizable material with the features according to the first part of patent claim 1.

E-PA-0148 966 discloses a continuous mixing and shear rolling mill for plasticizable material with two tempered rolls rotating in opposite directions at different peripheral speeds, the roll length of which is more than four times the roll diameter and on which sharp-edged grooves are located at an acute angle to the roll axes are arranged in opposite directions to one another, the number of grooves along the roller axes increasing from the bearing side with the material feed to the middle of the roller and decreasing from there to the bearing side with the material decrease, and material feed and removal devices for different material types and additives being arranged, which are adjustable in the axial direction along the nip.

The object of the invention is to further develop this continuous mixing and shear rolling mill, which has become known from EP-A-0148966, in order to achieve an optimal shear force effect on the material.

This object is achieved with the features in the characterizing part of the patent claim. Tests have shown that the melting behavior of the materials to be processed is very different.

Accordingly, there is an optimal groove geometry, an optimal temperature and an optimal shear force effect on the material for each material in the various states of solid, plastic or liquid.

It is envisaged that the friction ratio of the two shear rolls will periodically be changed considerably in a short rhythm in order to adapt to the plasticizing behavior of the material by a controlled change in the speed of the rolls.

During the processing time, a material particle moves, for example, from the feed side to the take-off side in 60 to 250 seconds. The speed behavior is periodically measured by the two shear rollers in a ratio of 5: 1 to 1: 5 in a time rhythm of e.g. Changed 5 to 50 seconds.

Accordingly, the material particle on its way in the kneading bead and on the roller is exposed to shear forces that change considerably several times.

The effect of this measure can also be seen externally from the changing size and direction of rotation of the material kneading in the shear gap.

In a further advantageous embodiment, the two shear rollers are equipped with different temperature zones along the path of the material. In the case of smaller machines, at least three different temperature zones are advantageous along the bale length of the rollers, and two in the case of larger rollers (approximately from 1500 mm bale length) at least three different temperature zones. They are achieved by separately supplying and discharging the various tempered liquids.

• Fig. 1 eine Längsschnittansicht durch ein temperiertes Walzenpaar eines kontinuierlichen Misch- und Scherwalzwerkes,
• Fig. 2 eine Ansicht auf ein Walzenpaar mit einer materialbedeckten Walze,
• Fig. 2a eine Draufsicht auf das Walzenpaar nach Fig. 2,
• Fig. 3 eine Draufsicht auf ein Walzenpaar mit einer mit Sacklöchern versehenen Walze,
• Fig. 3a ein Querschnitt im Bereich des Walzenspaltes durch das Walzenpaar nach Fig. 3,
• Fig. 4 eine Ansicht auf ein Walzenpaar mit einer materialbedeckten Walze,
• Fig. 4a eine Draufsicht auf das Walzenpaar nach Fig. 4 mit zonenweisen Nutenabschnitten mit einer Gegensteigung,
• Fig. 5 eine Ansicht auf ein Walzenpaar mit einer materialbedeckten Walze,
• Fig. 5a eine Draufsicht auf das Walzenpaar nach Fig. 5 mit zwei Gegenförderabschnitten auf einer Walze.
• Fig. 6 eine Draufsicht auf ein Walzenpaar mit auf beiden Walzen flexibel aufgereihten von verschieden genuteten Mantelabschnitten für die verschiedenen Materialien,
• Fig. 6a eine Längsschnittansicht durch die Walze 32 nach Fig. 6,
• Fig. 7 eine Draufsicht auf ein Walzenpaarabschnitt im Bereich der Abnahmezone mit einer dort wirksamen Streifenschneidwalze mit einer Querschneidvorrichtung zur Herstellung von Würfelgranulat,
• Fig. 7a eine Seitenansicht auf die Einrichtung nach Fig. 7,
• Fig. 8 eine Draufsicht auf ein Walzenpaarabschnitt im Bereich der Abnahmezone mit einer dort wirksam angeordneten Granulierzylinder zu Herstellung von Zylindergranulat,
• Fig. 8a eine Seitenansicht auf eine Einrichtung nach Fig. 8,
• Fig. 9 eine Draufsicht auf ein Walzenpaarabschnitt im Bereich der Abnahmezone mit einer dort wirksam angeordneten Abnahme- und Ausformschnecke zur Herstellung von Granulat und
• Fig. 9a eine zum Teil geschnittene Seitenansicht auf die Einrichtung nach Fig. 9.

Embodiments of the invention are shown in the drawings and are explained in more detail below. Show it

• 1 is a longitudinal sectional view through a tempered pair of rollers of a continuous mixing and shear rolling mill,
• 2 is a view of a pair of rollers with a roller covered with material,
• 2a is a plan view of the pair of rollers of FIG. 2,
• 3 is a plan view of a pair of rollers with a roller provided with blind holes,
• 3a shows a cross section in the area of the roll gap through the pair of rolls according to FIG. 3,
• 4 is a view of a pair of rollers with a material-covered roller,
• 4a is a plan view of the pair of rollers according to FIG. 4 with zone-wise groove sections with a counter pitch,
• 5 is a view of a pair of rollers with a roller covered with material,
• Fig. 5a is a plan view of the roller pair of FIG. 5 with two counter-conveyor sections on a roller.
• 6 is a plan view of a pair of rolls with differently grooved jacket sections for the different materials, flexibly lined up on both rolls,
• 6a is a longitudinal sectional view through the roller 32 of FIG. 6,
• 7 shows a plan view of a roller pair section in the region of the removal zone with a strip cutting roller effective there with a cross-cutting device for producing cube granulate,
• 7a is a side view of the device of FIG. 7,
• 8 is a plan view of a roller pair section in the area of the removal zone with a granulating cylinder effectively arranged there for the production of cylinder granulate,
• 8a is a side view of a device according to FIG. 8,
• 9 is a plan view of a roller pair section in the region of the removal zone with a removal and shaping screw for the production of granules and effectively arranged there
• 9a is a partially sectioned side view of the device of FIG .. 9

As shown in FIG. 1, the roller sections on the feed side 2.1 of the material 8.3 are heated such that the material 8.3 to be processed adheres to the surface of the roller 31.

In FIG. 1, the roller section of the feed side 2.1 is tempered by the lines 1.11 and 1.12. This section almost always has to be heated much higher than the middle zone 2.2 and zones 2.3 and 2.4.

In many cases it is useful to use a protective heater with infrared heaters 1.13 to increase the heating of the feed material 8.3.

In the roller section of the middle zone 2.2, some viscous materials 8.3 develop considerable frictional heat due to shear forces, which must be checked. For this purpose, the inner second temperature control zone with the inlet and outlet lines 1 .21 and 1.22 as well as the outer protective heating 1.23 are provided.

In the third roller section of zone 2.3, a reduction in the material temperature is controlled in most cases by the fact that heat is dissipated from the inside via the lines third temperature zones 1.31 and 1.32 and a fan cooling 1.33 is attached from the outside.

For thermoplastic materials, e.g. are melted from the powder or granular state, a significantly different groove geometry of the two shear rollers has proven to be advantageous.

The material-covered front roller 31 is equipped with grooves 35, the geometry of which varies considerably along the length of the bale, as shown in FIG. 2a.

In the area of material feed 2.1, grooves 35 of 0.5 to 20 mm, preferably 5 mm deep and 1 to 40, preferably 10 mm wide, are incorporated.

They are cut uniformly deep over a length of 25% to 30% of the bale and form the material feed and preheating zone 2.1, as shown in FIG. 2a.

In the middle zone 2.2, which makes up about 35% to 40% of the bale length, the depth of the grooves 35 is continuously reduced to about half the value of the material feed zone 2.1, preferably to 2.0 to 2.5 mm depth, as in the case of a core-progressive screw. It is advantageous for some materials that are very tough to double the number of grooves 35 to improve the material transport.

In the third roller section of the homogenization zone 2.3, which accounts for approximately 25% to 30% of the bale length, the material is homogenized and often cooled 8.3. The depth of the groove 35 is continued from the outlet of the core-progressive middle zone 2.2 to the groove outlet.

The material cooling in the third and fourth roller sections, in the homogenization zone 2.3 and in the removal zone 2.4 reduces the tendency to stick to the rollers 31 and 32. At lower temperatures, the material strength also increases.

This facilitates the removal of the material 8.3 as strips and prevents the granules from sticking together during granulation.

The removal zone 2.4 is expediently carried out with approximately 10% to 15% of the bale length on both rollers 31 and 32 without grooves 35 and 36.

The tests showed that with materials 8.3 with a higher melting and softening range, the generation of a plastic material covering on the work roll 31 sometimes causes problems, as long as the material temperature in the application zone 2.1 is not yet high enough, on the grooves 35 and the surface to cause sufficient material liability. Additional frictional heat can only be introduced into adhesive plastic material layers via shear forces. In this way, friction between plastic layers can achieve much higher energy generation than friction between plastic and metal surfaces.

On the basis of this observation, the smooth web surfaces 38 between the inclined grooves 35 are provided with a plurality of material holes 3.1 as dimples in the feed and mixing area of the roller 31, as shown in FIG. 3.

A small cylindrical section of the hole with a depth of 0.5 to 10 mm, in particular a depth of 1 to 2.5 mm, merges into a flat-angled hole base 3.3 (e.g. of 120 ° or a corresponding flat rounding of the hole base 3.3).

The hole diameter is 2 to 20 mm, preferably 3.5 to 5 mm with a total depth of approx. 2 to 3 mm.

The ratio of the hole diameter to the hole depth is to be dimensioned such that, on the one hand, due to a somewhat longer dwell time of the material 8.3, the material 8.3 temporarily adheres or melts in the blind hole 3.1, and on the other hand, through the counter-roller 32, enough new, colder material 8.3 Exchange of the hole content is pressed.

The blind holes 3.1 improve the adhesion of the material covering of the roller 31 by mechanical clamping and additionally form heat exchange surfaces.

When the blind hole 3.1 enters the kneading gap 37 of the rollers 31 and 32, the gap pressure builds up fully in this area because no pressure relief can take place in the closed system; the shear energy and vortex movement in the hole bottom 3.3, which can be introduced locally by friction, is correspondingly large, as shown in FIG. 3a.

In difficult cases it is useful to provide the web surfaces 38 of the material-free roller 32 with blind holes 3.1 of the type described above. However, with the same hole diameter, they may only be at most about half as deep as the blind holes 3.1 on the work roller 31, so that they do not cancel out the greater material liability on the roller 31.

The shear roller system only works with an oppositely driven, equally grooved roller 32, which forms the other part of the shear or roller gap 37 without material support.

The task of the grooves 36 in the counter-roller 32 is to introduce the shear forces into the outer layer of the material-covered front roller 31, to introduce new material 8.3 into this layer and to generate the material shear force along the material kneading.

The depth of the grooves 36 of the counter-roller 32 is kept much smaller than in the material-covered front roller 31. This groove depth is at about half of the working or roller gap 37, for example between 1 and 3 mm. The counter-roller 32 is grooved at a depth from the feed zone 2.1 to the smooth outlet in the removal zone 2.4.

With the aid of these grooves 36, the addition material 8.3 is drawn into the nip 37 and there intimately mixed with the plastic material 8.3, or embedded in the plastic material layer 8.3. These grooves 36 push the material 8.3 over the groove angle in the kneading and on the work roller 31 in the direction of the take-off side 2.4, if both rollers 31 and 32 are driven in opposite directions and also have an opposing groove angle.

Experiments led to a further advantageous step in that groove sections 4.2 with a counter pitch are arranged on the roller 32 to increase the mixing effect, as shown in FIG. 4. The counter slope of the grooving produces kneading vortices 4b rotating in opposite directions locally perpendicular to the roller gap 37, as shown in FIG. 4a.

The zones of the counter slope may only be short, because otherwise the entire material transport in the kneading or roller gap 37 in the direction of the removal zone 2.4 comes to a standstill.

As a rule, at least two counter-conveying zones 4.1 and 4.2 are arranged in the roller 32, which, however, should only have a length of 0.25 to 1 times the roller diameter and must have intermediate sections with a strong conveying pitch of at least one or two roller diameters in length.

5, the roller 32 is equipped with two larger counter-conveyor sections 4.3. While the roller 31 is covered with material 8.3, a liquid is left at points A and B, e.g. Oil in rubber processing or a liquid stabilizer B in the kneading or roller gap 37. As long as the two rollers 31 and 32 are rotating, the liquid is conveyed against each other by the opposite groove increase and reaches the material to be processed 8.3 via the vertical material vortex.

In this way, two mountains of liquid can be maintained in the gap 37, which are so high that the excess liquid can pass laterally over the rollers 31, 32 and the amount of liquid absorbed can be detected by differential weighing.

From the various steps described above it follows that, in order to optimize the rollers 31 and 32, a design was developed which allows the optimal groove geometry to be tested for the different materials by flexibly lining up different grooved jacket segments 4.1, 4.2, 4.3, 4.4, as shown in FIG. 6.

In this case, the various jacket segments 4.1, 4.2, 3.4, 4.4 are axially lined up and tested on the tempered roller cores, the rollers 31 and 32 being able to be fitted with the various segments as desired, as can be seen from FIG. 6a.

For the material removal 2.4, the grooves 35, 36 run out in a smooth roller section (2.4) with about 10% of the bale length. In this area, the processed material 8.3 is removed, as the following FIGS. 7 to 9a show.

The material is removed as strips 7.1 with a strip cutting roller 7, as shown in FIG. 7. It is equipped with round knives 7.6 and driven with a pair of gearwheels 7.2 from the roller 31 at a somewhat higher speed (approx. 5% to 10% advance). Depending on the number of circular knives 7.6, several strips 7.1 are produced at the same time, which are cut into cube granules 7.5 in a cross-cutting device 7.4 with removal block 7.3 and knife roller.

In another advantageous embodiment, according to FIGS. 8 and 8a, a driven hollow cylinder 8.1 is pressed against the plastic material layer of the roller 31. The outer circumference of the cylinder 8.1 contains a plurality of bores 8.2 through which the plastic material 8.3 is pressed into the open interior. There is a cooled knife 8.4, which cuts off the pressed-through rod sections as cylindrical granules 8.5. To cool the hollow cylinder 8.1 and the granulate material contained therein), the outer jacket runs through a shell 8.6 filled with water or other coolant.

In a further variant, tough plastic and very sticky materials 8.3 are removed from the roller 31 with a removal and shaping screw 9.0, as shown in FIGS. 9 and 9a. It is arranged from the outside with its adapted cylinder opening 9.1 vertically up to a small distance from the material-covered roller 31. The webs 9.3 of the rotating screw 9.0 scrape plastic material 8.3 down from the smooth roller section 2.4 and feed it to a molding die 9.4. There it is then further processed with known granulating or profiling devices.

Claims (9)

1. Continuous mixing and shearing rolling mill for plasticisable material with two tempered rolls (3, 32) which rotate in opposite directions at differing peripheral speed, the length of said rolls being more than four times the roll diameter and said rolls having arranged on them sharpedged grooves (35, 36) running in opposite directions from one another at an acute angle to the roll axes, whereby the number of grooves (35, 36) on the circumference of the rolls and the depth of the grooves (35, 36) along the axes of the rolls increases from the bearing side with the material feed (2.1) to the middle of the rolls and from there, decreases again to the bearing side with the removal of material (2.4), and with devices for feeding and removing the material, said devices being adjustable in an axial direction along the roll gap (37) and being suitable for various types of material and additions, characterised in that the speed ratio of the two rolls (31,32) is altered periodically in the ratio of 5:1 up to a maximum of 1:5 in a time rhythm of 5 to 50 seconds.

2. Continuous mixing and shearing rolling mill as claimed in Claim 1, characterised in that to suit the melting behaviour of the material (8.3) the two rolls (31,32) are tempered through the inner tempering (1.11, 1.12, 1.21, 1.22, 1.31, 1.32) and through the external radiation heating (1.13,1.23) to different temperature levels along the surface length of the rolls (31, 32).

3. Continuous mixing and shearing rolling mill as claimed in Claims 1 and 2, characterised in that the front roll (31 ) which is covered with material is given a groove geometry along the surface length of the roll, with which in the material-feed zone (2.1 ), with about 30% of the surface length the grooves (35) are cut particularly deep, in the middle zone (2.2) with about 35% of the surface length, the grooves (35) are reduced progressively with the core to the flat groove depth of the homogenising zone (2.3) - approximately to half the value -, and in the take-off zone (2.4) of the material, which follows the homogenising zone (2.3) with about 25% of the surface length, both rolls (31, 32) are executed without grooves (35, 36) over a surface length of about 10%.

4. Continuous mixing and shearing rolling mill as claimed in one of the Claims from 1 to 3, characterised in that the smooth crosspiece surfaces (38) between the grooves (35, 36), particularly on the front roll (31 ) which is covered with material in the material-feed zone (2.1) and in the middle zone (2.2), are provided with a plurality of flat blind holes (3.1 ).

5. Continuous mixing and shearing rolling mill as claimed in one of the Claims from 1 to 4, characterised in that the rear roll (32) is equipped with one or several short counter-conveying zones (4.1,4.2) of about 0.25 to 1 roll diameter in length between interposed sections (4.3) with a strong conveying action.

6. Continuous mixing and shearing rolling mill as claimed in one of the Claims from 1 to 5, characterised in that for the front roll (31 ) and for the rear roll (32), on the tempered roll bodies, axial surface segments (4.1,4.2,4.3,4.4) are lined up which are designed differently as regards length, depth of groove and slope of groove.

7. Continuous mixing and shearing rolling mill as claimed in one of the Claims from 1 to 6, characterised in that in the take-off zone (2.4) material (8.3) arriving in stripform is taken over by a counter-positioned, driven and cooled take-off roll (7) which is designed such that it serves as a counterbearing for a cutter rolling device which is also driven with this, and in that the circular blades (7.6) divide the material (8.3) into narrow longitudinal strips (7.1) which are subsequently cut up by a transverse cutting device (7.4) into cube- shaped granulates (7.5).

8. Continuous mixing and shearing rolling mill as claimed in one of the Claims from 1 to 6, characterised in that material (8.3) arriving in the take-off zone (2.4) is pressed by means of a counter-positioned, additionally cooled granulating cylinder (8.1) through bores (8.2) on the cylinder surface and is cut on the inside by cutting blades (8.4) into cylindrical granulates (8.5).

9. Continuous mixing and shearing rolling mill as claimed in one of the Claims from 1 to 6, characterised in that material (8.3) arriving in the take-off zone (2.4) is taken off by a rotating worm (9.0) and transferred into a spiral cylinder (9.1) in order then to be pressed out through a forming-out device (9.4), and in that the worm (9.0) and the spiral cylinder (9.1) are positioned from outside at a perpendicular angle in relation to the front roll (31).

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